Process for the recovery of organic compounds from photographic solutions



Sept. 12, 1944.

K. J. BRUNINGS PRECIPITATOR -1 Q? /ACID GENERATOR Q Q' 1 I 26 33- SEPARATORS PR 4| CENTRIFUGE PREC'P'TATOR MIXER {UNIT )v N-J 33 ATTO EYS Patented Sept. 12, 1944 UNITED STATES. PArENromce PROCESS FOR THE RECOVERY OF ORGANIC COMPOUNDS FROM PHOTOGRABHIC SO- LUTIONS Karl J. Brunings, Rochester, N. Y., assign'or to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey I Application February 20, 1941, Serial o. 379,905

6 Claims. (c 260-574)- This invention relates to the recovery of organic compounds from solutions obtained from various photographic processes. More particularly this invention relates to the recovery of tical conditions may be present in the form of free bases. In commercial operations, and in particular in continuous photographic processes, the overflow from these continuous processes contains large amounts of these soluble compounds, and although the solution itself is near exhaustion, or otherwise inefiective due to the formation of various products during the continuous process the compounds themselves may still be used if they can be removed from the solution. Continuous development forms no part of the present invention and is merely mentioned herein to designate one common type of process from which solutions are obtained containing valuable components, heretofore, lost, but from which may be recovered valuable organic compounds, in accordance with my invention.

Further details respecting continuous development are set forth in the article published in The Journal of the Society of Motion Picture E ng. 31:273-86, 1938. It is there pointed out in order to maintain relatively constant and uniform conditions, a certain amount of materials may be added to the photographic baths and a certain quantity of the solution withdrawn. In solutions from this general type of process, as well as other solutions from photographic processes, there are present varying amounts of valuable organic compounds. In view of the fact that these compounds may be in admixture with other compounds and in diluted condition many problems are presented in recovering the valuable materials in a satisfactory manner. Consequently, in the prior art in many instances large amounts of these compounds have been lost by discharge to waste, because no satisfactory recovery method existed.

It isapparent that the formulation of an economically feasible recovery process which may also include steps of separating of the compound which it is desired to recover from other compounds, represents a highly desirable result.

This invention has for one object to provide a process for separating and recovering organic compounds from various developer solutions and the like. A still further object is to provide 'a recovery method for treating photographic solutions to recover organic compounds, therefrom,

and particularly overflow solutions from con;- tinuous developing processes. A still furtherobe ject is to provide a recoveryprocess for obtain- 2 ing from developer solutions recovered organic compounds which may be reutilized in preparing further developer solutions. Still another object is to provide a novel 'recovery'methodwhich, is

particularly adapted to the recovery of developing agents from Twaste, discarded and/oroverfiow solutions from developing processes which, processes may be handling either black-and-white or. color development Still another objectistopro vide a recovery process forrecovering organic developers, antifogg'ants, and the like organic,

compounds used in photographic processes, in a solid state either similar or. identical to the origir nalsubstances used. A stillfurtherobject'is tov providev apparatus arrangements particularly suitable for carrying out the aforesaid steps.

rials. Whilemy process functionssatisfactorily in the recovery of various differenttypes of the organic compounds used in photographic. proc-, esses in discussing the present invention reference will be made in manyinstances to certain of the general characteristics of thecompounds and type of solutions which may be encountered industrially, and from which it may be desired to separate and recover developers, antifoggants, and the like.

As indicated above, many agents;- organic alkalies, chemical fogging developing agents, and antifoggants used in photographic processes, are organic bases. The specific chemical structure of these compounds may vary, but in general it usually may be said that they may be classed as aromatic compounds. For example, more than seventy-five specific compounds are described in French Patent 804,472, relating to developers and the like. Or reference maybe made to U. S. Patent 2,115,394 where anumber of diiferent organic compounds which function as developers in color-photographic processes are indicated. Reference to U. S. Patent, 2,150,702 illustrates a number of organic compounds which are antifo'ggants. The foregoing have been set forth merely for general illustration, no attempt being made to enumerate every possible developer or other organic compound but the aforementioned-citations indicatein general way the type of compound and solution to which my process may be applied. I

It will be observed from the consideration of ofthe developing the foregoing that in many instances the organic compounds in the solutions from photographic processes, whether developers or antifoggants are aromatic compounds having at least one hi I trogen atom in the molecule. ,More particularly,

ing crystallization, evaporation, or'precipitation,

' the latter being preferred for reasons which will in many instances, the compounds are amino compounds from the group consisting of aminophenol and diamines, and especially derivatives thereof. of phenylenediamines wherein the substituents may not only be in the amino groups but may also be on the nucleus, as phenylenediamine For example, there are the derivatives tracts used. However, this method be set forth hereinafter. The organic compounds may also be removed from their solvent solutions by reextraction with, for example, diluted or concentrated acids, and the resultant exanalysis and neutralization of the extract, hence, involves problems of standardization and consequently I, prefer the precipitation procedure which will be illustratedin further detail.

compounds having alkyl groups both in an amino' group and'attached to the benzene nucleus. In

development andfthe production of the solutions containing thesel valuable organic components which I'have discovered 'mayibe satisfactorily separated and recovered in the solid state, similar or identical to. the original substances. How ever, the exact mannerof the obtaining of such solutions is not a limitationuponmy invention.

The aforementioned reference to using my in: vention in treating the solutions from continuous developing processes has been alluded to inasmuchasit constitutes one important sourceof solution which may" be treated, and illustrates how, my'process may be used in conjunction with other commercial processes It is suiiicient to merely state thatithe solution from which it is desired to separate and recover theorganic' compoundsis obtained from'some source, ascontinuous'processing, and placed in feed tanks which feed into my'process. Preferably in the instance where there aresolutions from several different sources in sufllcient quantities, the solutions would be treated independently "in myprocess and in some instances a particular solvent might be used for-each solution'or other steps adopted, permitting not only the recovery-of, for example, the developer present-in the solution, but also, rendering it possible to treat the residue from my processin amanner where'still other components may be recovered. The use. of a particular $01 vent for any specific solution sometimes, also gives still improved results. 7

' Referring now'to more specific features'of my invention, I have 'found that at high pHs the organic compounds which have been discussed (organic bases) "have on'lya' minimum solubility in water and maybe extracted from-their solutions with variousaro'matic solvents, hydrocarbons, ethers, esters, and halogen solvents. That is, in accordance with my novel procedure, these organic compounds (organic bases) may be recovered andmcollected in a more concentrated form; If the solution'in question is already alkaline, extraction withthe solvent in accordance with my invention 'may he proceeded with dif the solution to which my recovery process is to be applied is not in the proper pH condition as obtained, suitable additions are made, as for My preferred method employing precipitation involves the principle that organic bases, dissolved in an inert solventmay be precipitated in the form of their acid salts'by treating'the solutions with gaseous, liquid or solid anhydrous acids, and/or acid anhydrides. The acid salts of the organic bases thus formed are generally completely insoluble in the organic solvent and precipitate outin an easily filterable condition.

By my novel procedure the organic constituents being recovered are retrieved in a solid state either identical to the substance used and, in general, free from undesired components as harmful oxidation products. The recovered product may be used in subsequent mixes without 7 material changes in formula, and without previous tedious analytical assays. In other words, by my preferred method the compound'recovered from the overflow solution can be used in preparing fresh quantities of the initial solution because the compound is in a state particularly suitable for this use.

For further understanding of my invention reference will be made to theattached drawing,

forming a part of the present application. Fig.

1 is a semi-diagrammatic side elevation view, showing one arrangement of apparatus which might be employed for carrying out my process.v

Fig. 2 is likewise a semi diagrammatic side elevation view showing one type of change which might be made in my apparatus set-up. It will be noted that the drawing is also somewhat in the nature of flow sheets of my process.

Referring now to Fig. 1, 2 is the feed conduit through which the material to be subjected 'to recovery is supplied to the system. In general the feed will comprise an aqueous solution. This conduit discharges into the unit 3 positioned upon support 4. The device 3 may comprise a conventional mixer or other type of device for bring ingthe solution in intimate contact with the extracting agent. The showing in Fig. 1 is merely diagrammatic. While the unit hasbeen shown inan elevated position, in order that gravity flow from the apparatus may take place it is possible to place it in a lower position and pump the fluids therefrom. LAISO more than one extractor or mixer unit may be employed. Feeding into the mixer or extractor 3 is another conduit 6 which is connected through pump I to the solvent tank 8.

Leading from an intermediate point in mixer 3 is another conduit 9 which goes to the several separator H, l2, and I3. These separators are interconnected in series by means of the conduits l5 and I6. Also, further connections may be made as at l8 and 19. These separators are of the gravity type, being merely elongated chambers in which liquid of the lowest specific gravity becomes the top layer and the liquid of higher specific gravity the lower layer. the units may be considered more or' les comparable to decanters. Suitable provision, not shown, may be made whereby the liquid residue involves In other words 7 in the bottom of the separators may be discharged to other treatment or to waste.

The exact number of separators which would be I employed, and also the employment of some of the separators in parallel or inbatteries, if this be desired, in order that units may be cut out of or into operation without stopping the process, is within theorbit of the present invention; Such features may be employed, depending upon the materials treated and the type of operation, continuous, semi-intermittent, or a batch, of the combination of such operations which may be desired. r

In any event usually I prefer that the terminal unit in the group discharge through conduit I! through drier I4 and conduit 2| "into the unit designated 22 and termed a precipitator. This later unit may be placed on a support 23 for facilitating access to the lower portion thereof for removing the contents through conduit 24. Conduit 24 feeds through pump 26 in series and positioned before filter presses orother similar devices 21. Although only one unit has been indicated at 21 it is to be understood that there may be'several units in the group so that when one filter press is removed from operation other units may be put into operation without a discontinuance of the process. It also is to be understood that other devices, such as thickeners, may be employed for removing the precipitate from the liquid containing it. However accomplished the liquid (solvent) separated in 'unit 21 may be returned through conduit 28 to tank 8.

Referring back to precipitator 22, connected therewith by means of conduit 29 is a unit designated 3| for generating precipitating agent. The exact, construction of this unit would depend upon the particular type material which was to be generated and introduced a substantial distance into the precipitator by means of the internally extending distributing means 32. 'For example unit 3| might comprise more or less a standard hydrochloric acid gas generator such as aKipp type generator, operating on ammonium chloride. However, I prefer to operate a type of generator which generates hydrogen chloridevapors from concentrated sulphuric acid, mixed with concentrated hydrochloric acid. Of course, if sulphurous acid vapors or acid anhydrides were to be generated, the exact construction of part 3| would be such as to enable the production of the desired acid and/or anhydride and inject into the precipitator.

Referring back to the mixer and separators, there is connected therewith conduit 33 through which residue components from these units may be withdrawn to further recovery steps or other treatment. I

Referring now to Fig.2, I show in this figure'an example of one modification which, in addition to those already referred to may be made in my ap paratus arrangement. In this set up 3 represents the mixer already discussed above. However, in this arrangement, a'conduit .41 leading from an intermediate point in the mixer instead of being connected with the separators, as discussed above under Fig. 1, is connected to one or more centrifuge units 42. may be of conventional spinning type. In function the centrifuge may be considered merely as gravity separation speeded up. Under some circumsta'nces, for increased capacity or in the handling of extracted mixtures which do not readily or quickly separate by gravity, it, may be desirable to employ forced separation rather than gravity separation. However, I have found that in most The centrifuge .units instances gravity separation suffices and is simpler more economical, and is satisfactory. In this arrangement the centrifuge would discharge through the line 43, pump 44, conduit 45, and into precipitator 22. This precipitator 22 has already been described under Fig. 1, hence, further description is unnecessary, it merely being indicated that the precipitator connected with the other unit as already discussed.

If desired, a drier comparable to drier 14 in Fig. 1 could be inserted at some point in the circuits 43, 44, and 45. However, after employing forced separation the subsequent drying step may sometimes be eliminated or reduced tosuch an extent that a smaller drier than [4 may be employed. In any event the dryin unit may comprise simply one or more columns containing a. hygroscopic substance, such as calcium chloride or other drying. agent,

Sight glasses, valves and the like may be in.- cluded in the apparatus as desired and an invention is not to be restricted in this respect.

The operation of my apparatus arrangement as well as a better understanding of my process will be had from. the'consideration of the followin example. This exampleis set forth primarily for illustrating one preferred embodiment of my recovery process, hence, is not to be considered a limitation upon my invention. i

In this example the solution to be subjected to my'novel recovery procedure contained an orgame developer. The particular developer was an 'cordance with the preceding description and might be considered a derivative of phenylenedi amine in which alkyl groups had been substituted \for hydrogen in the amino group and/or at other points in the molecule. The particular nature of the compound, as already pointed out, is not a limitation upon my invention, the process as described in this particular specific example functioning equally well with other-amino compounds such as phenylenediamine derivatives and aminophenol derivatives; The pH 'of the aqueous developing solution necessary for the extraction is dependent upon the type of compound to be recovered, andthe efficiency of extraction desired. The solutions to be treated in this example were held at a fall between 10.5 and 11.5.

'-In brief, the process applied to this solution from which it was desired to recover the amino organic developer was as follows:

(1) The solution was violently stirred with a hydrocarbon solvent. In this particular instance the solvent employed was kerosene of a high flash point, obtained commercially from one of the large oil companies. This solvent chemically was usually comprised principally of straight chain hydrocarbons '(dodecane through pentadecane) and also included a few percent of components such as cyclic hydrocarbons and aromatics. Trade names of these petroleum cuts are Stoddard 'Solvent, Sunoco Spirits, etc. It is to be understood that other hydrocarbon solvents could be employed, such as the aforementioned ingredients in pure condition. Inasmuch as a commercial material such as kerosene functions satisfactorily, there is economically no reason to go to more expensive solvents, but it is desired to make it clear that my invention is not limited in this respect. The aforementioned procedure was carried out in mixer 3 of Fig. 1, the kerosene being introduced through conduit 6 from tank 8 and the solution introduced through the feed conduit 2.

In the eventthat another acid medium was employed as a precipitant it is to be understood that suitable materials would be employed for resisting that particular acid. In some instances acid resistant stainless steels are employed and in other instances the equipment may be constructed of metal-clad, glass or rubber lined parts, depending upon the corrosive nature of the solutions being handled. It is, of course, understood that materials injurious to photographic chemicals would not be employed. As already described, I may employ various organic and inorganic acid materials for carrying out the precipitation step, ranging from common acids such as hydrogen chloride, sulphuric acid, to the less common acids such as phosphoric acids and/or the anhydrides of any of the foregoing and various mixtures.

Likewise, a variety of solvents may be employed. I have tried numerous solvents and, as indicated, have found many to be satisfactory from the standpoint of extraction and precipitation. Kerosene (Stoddard Solvent, Sunoco Spirits, etc.,) has the advantages of relatively low cost, non-toxicity, and high flash point. The ethers such as diethyl or isopropyl and higher ethers, and dioxane, also have been found useful in many instances. Benzene, toluene and xylene give good results from the chemical standpoint. Esters such as the ethyl acetate, butyl butyrate, and other esters serve as good extracting solvents. All of the latter are good solvents for the phenylenediamine type of developer. For the aminophenols and phenyl derivative types of compounds ethers and esters have been employed with good results. Other petroleum cuts are satisfactory for phenylenediamines exemplified by ligroin and petroleum ethers. As set forth in the preceding examples, when the phenylenediamine type of developer is recovered I would generally use commercially obtainable, low cost hydrocarbon exemplified by kerosene. In the instance of the recovery of other types of organic compounds I might prefer, for example, ester or ether such as di-isopropyl, diethyl ether, butyl acetate for the recovery of the phenolic type or the aminophenolic type of compounds. Or in the recovery of the phenylenediamines type of organic compound I might employ an aromatic type of solvent.

It is, therefore, apparent from the foregoing that my invention is susceptible of modification. Hence, I do not wish to be restricted excepting insofar as is necessitated by the prior art and the spirit of the appended claims.

What I claim and desire to be secured by Letters Patent of the United States is:

1. The process for the recovery of aromatic amino photographic agents contained in aqueous solutions derived from photographic processes, which comprises intimately mixing said .solutions with a solvent essentially consisting of kerosene to obtain an extract, withdrawing the extract and subjecting it to separation steps, withdrawing the extract from the last separation step and drying the same, bringing the dried extract into intimate contact with acid materials to cause the formation of a precipitate, and subjecting the precipitate to filtering operations for separating it from the solvent whereby the solvent may be returned for reuse in the process.

2. A process for the recovery of aromatic amino photographic agents contained in aqueous solutions used in photographic processes, which comprises mixing the solution with a solvent for the organic bases essentially consisting of kerosene, separating an extract layer comprising said solvent and the organic base extracted therein from at least a part of the other components, subjecting these extracted materials to a plurality of separation steps wherein the solvent, having the organic base extracted therein, is still further separated from the other materials, drying the resultant extract by contact with a dry-' ing medium, and subjecting the dried extract to intimate contact with a dry acid gas bubbling therethrough to cause the formation of a precipitate comprising at least one of said organic bases and filtering the resultant mixture to obtain the separation of the precipitate from the solvent.

3. In a process for the separation and recovery of aromatic amino photographic agents present in aqueous solutions from continuous photographic processes, by procedure including rendering the solution alkaline, the steps which comprise extracting said photographic materials from the aqueous solution by a solvent therefor essentially consisting of kerosene, separating and drying the extract and precipitating the photographic materials from the extract by introducing into the extract a dry acid gas.

4. The process for the recovery of derivatives of phenylenediamine contained in aqueous solutions obtained from photographic processes, which comprises intimately mixing said solutions with a solvent essentially consisting of kerosene, withdrawing the extract obtained thereby and subjecting it to separation steps, withdrawing the extract from the last separation step and drying it, bringing the dried extract into intimate contact with acid materials to cause the forma-- tion of a precipitate, and subjecting the precipitate to filtering operations for separating it from the solvent, whereby the solvent may be returned for reuse in the process.

5. The process for the recovery of aromatic amino photographic agents of the amino phenol type contained in aqueous solutions obtained from photographic processes which comprises intimately mixing said solutions with a solvent essentially consisting of kerosene, withdrawing the extract obtained thereby and subjecting it to separation steps, withdrawing the extract from the last separation step and drying it, bringing the dried extract into intimate contact with acid materials to cause the formation of a precipitate, and subjecting the precipitate to filtering operations for separating it from the solvents, whereby the solvents may be returned for reuse in the process.

6. The process for the recovery of aromatic amino photographic agents contained in aqueous solutions derived from photographic processes, which comprises intimately mixing. said solutions with a solvent essentially consisting of petroleum hydrocarbons boiling within the range 40-300" C. to obtain an extract, withdrawing the extract and subjecting it to separation steps, withdrawing the extract from the last separation step and drying the same, bringing the dried extract into intimate contact with acid materials to cause the formation of a precipitate, and subjecting the precipitate to filtering operations for separating it from the solvent whereby the solvent may b returned for re-use in the process.

KARL J. BRUNINGS. 

